1. Field of the Invention
The present invention relates to a sheet discharge apparatus for giving a wavy shape to a sheet and discharging the sheet, and an image forming apparatus with the sheet discharge apparatus mounted thereon, such as a laser printer or copying machine.
2. Description of the Related Art
An image forming apparatus such as a laser printer includes: an image processing mechanism for forming an image on a recording sheet; a conveyance passage for conveying the recording sheet with the image formed thereon; and a stacker for accumulating the recording sheets discharged from the conveyance passage. The image processing mechanism, conveyance passage and stacker are incorporated in a box-shaped apparatus body.
In this type of image forming apparatus, when a large amount of recording sheets are continuously conveyed, the recording sheets discharged from the conveyance passage are successively stacked and stored in the stacker. The recording sheet is thin and soft, and therefore inevitably curled, warped and deformed in the process of formation of the image or conveyance through the conveyance passage. When the recording sheets discharged from the conveyance passage are deformed in this manner, and stacked up in the stacker, the recording sheets are sometimes not aligned. As a result, the recording sheets are stacked up on the stacker in a disorderly manner, therefore look untidy, and cannot easily be removed from the stacker.
As an improvement measure, in the conventional image forming apparatus, a pressure is applied and a wavy shape is given to the recording sheet discharged via the conveyance passage by a plurality of rollers. Thereby, the recording sheet temporarily becomes rigid, and curls and deformation of the recording sheet are corrected. A concrete constitution for waving the recording sheet is disclosed, for example, in “Jpn. Pat. Appln. KOKAI Publication No. 9-301590”, “Jpn. Pat. Appln. KOKAI Publication No. 8-157125”, and “Jpn. Pat. Appln. KOKAI Publication No. 6-127776”.
On the other hand, in this type of image forming apparatus, a so-called in-body discharge type is known in which a space for discharging the sheets is secured inside the apparatus body. The space for discharging the sheets is connected to the downstream end of the conveyance passage, and opened to the outside of the apparatus body. For the image forming apparatus, in order to perform an efficient sheet discharge operation, a pair of stackers, and a separator unit for distributing the recording sheet to either one of the stackers are disposed in the space.
The stackers are stacked up and disposed in the height direction of the apparatus body. The lower stacker is disposed in a position lower than the downstream end of the conveyance passage. The upper stacker is disposed in a position higher than the downstream end of the conveyance passage.
The separator unit includes a gate for switching the discharge direction of the recording sheet, and a guide passage connected to the upper stacker. The gate can be rotated between a first changeover position and a second changeover position. When the gate is rotated into the first changeover position, the recording sheet discharged in a horizontal direction from the conveyance passage is guided into the lower stacker. When the gate is rotated into the second changeover position, the recording sheet is guided into the guide passage via the gate. The guide passage guides the recording sheet discharged from the conveyance passage to the upper stacker. Therefore, the guide passage extends in a vertical direction, and has two corner portions midway. One corner portion is positioned in the upstream end of the guide passage, and guides upwards the recording sheet discharged in the horizontal direction from the conveyance passage. The other corner portion is positioned in the downstream end of the guide passage, and guides the recording sheet conveyed upwards along the guide passage horizontally toward the upper stacker.
Since the separator unit needs to be contained in the limited space of the apparatus body, particularly the total length of the guide passage is shortened. As a result, two corner portions for changing the conveyance direction of the recording sheet are disposed in the vicinity of each other, and the guide passage is steeply bent in a crank shape. Therefore, the recording sheet is forcibly bent twice while passed through the guide passage.
The recording sheet is pressed by the plurality of rollers and waved before being guided into the guide passage. When the waved recording sheet is passed through the guide passage, a force for forcibly deforming the sheet is applied to the temporarily rigid recording sheet. Thereby, the recording sheet generates a harsh sound as if something were broken. This abnormal sound makes a noise, and may discomfort the operator.
Furthermore, when the recording sheet is passed through the guide passage, the force for forcibly stretching the sheet flat is applied to the waved recording sheet. As a result, the recording sheet is not smoothly conveyed, and therefore wrinkled, and jamming is caused.
Jpn. Pat. Appln. KOKAI Publication No. 6-239002 discloses an improvement in waving the recording sheet discharged from the conveyance passage. In this prior art, a hump member for pressing the recording sheet is disposed in the downstream end of the conveyance passage. The hump member can selectively move to a raised position or a lowered position. When the hump member reaches the raised position, the hump member juts out on the conveyance passage, and presses the recording sheet. When the hump member reaches the lowered position, the hump member retreats from the conveyance passage. Therefore, the recording sheet is discharged from the conveyance passage without being hampered by the hump member.
However, in the prior art, a sheet discharge apparatus is assumed in which a sorter is selectively connected to the downstream end of the conveyance passage and used there. In detail, it is detected whether or not the sorter is connected to the downstream end of the conveyance passage, and the hump member is moved in accordance with the detected result. Therefore, in the prior art, the problem of the abnormal sound generated by the recording sheet during the guiding of the waved recording sheet through the bent guide passage is not recognized, and the necessity of muffling the abnormal sound generated by the deformation of the recording sheet is not taught.